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प्रश्न
Five years ago, a man was seven times as old as his son, while five year hence, the man will be four times as old as his son. Find their present age
उत्तर
Let the age of a man be “x” and the age of a son be “y”
5 years ago
Age of a man = x – 5 years
Age of his son = y – 5 years
By the given first condition
x – 5 = 7(y – 5)
x – 5 = 7y – 35
x – 7y = – 35 + 5
x – 7y = – 30 → (1)
Five years hence
Age of a man = x + 5 years
Age of his son = y + 5 years
By the given second condition
x + 5 = 4(y + 5)
x + 5 = 4y + 20
x – 4y = 20 – 5
x – 4y = 15 → (2)
(1) – (2) ⇒ – 3y = – 45
3y = 45
y = `45/3`
= 15
Substitute the value of y = 15 in (1)
x – 7(15) = – 30
x – 105 = – 30
x = – 30 + 105
= 75
Age of the man is 75 years
Age of his son is 15 years
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